Keying



April 11, 1939. 1 ussl-:LMAN

KEYING Filed June l0, 1956' 2 Sheets-Sheet l N 5 mm M IW. mm k @$5 mw. Y|||| m m 1 V F lx A E v f m E l u il n m H www u .o m Qwqwb ..1 .Q H X n o wzmmk .mwwwww NN l ATTORNEY April 11, 1939. G. Ussl-:LMAN

KEYING 2 Sheets-Sheet 2 Filed June lO, 1936 m xmv W hpv l /w. R M Y N\ u O M E lw. b ma m l W S o H E Mwm ein' a u 1 I bv. B v rl MEW. TY m" NA M N\ m e m .Q u m Oll- `NH l n IO H n NMA." .Q u "W w @1w .Il m WN u. N .l 0 olI m Q .o m MN x .S 4P mm bn E s S m n m E Hes@ MN5. :n. mwhx N Patented Apr. 11, 1939 UNITED STATES PATENT oEFlcE KEYING Application June 10, 1936, Serial No. 84,435

' '1o' claims. (ci. ris-66) 'nils invention involves a novel method of and means for keying oscillatory energy. More in particular this invention involves the method of and means for keying the potential of the suppressor grid of an electron discharge tube of the pentode type the other electrodes of which are connected in alternating current circuits adapted to operate at signalling frequencies. By applying a negative voltage to the suppressor grid of a pentode tube the operativeness of the tube which may be included in a transmitter stage is controlled.

Other methods of and means for keying tube transmitter stages known in the art operate on l5 the control grid or screen grid potential. These methods and means produce considerable reaction on the transmitter driving stage whereas the present method and means of my invention has little or no eifect on the transmitter driving stage or preceding stage. l

In describing my invention reference will be made to the attached drawings through which like reference characters indicate like parts and in which,

Figures 1 and 2 show for purposes of illustration, circuit arrangementsincluding means for relaying and amplifying waves of carrier irequencyand for keying the same. The keying in both modifications is accomplished in a pentode ao stage and where several of the tubes are operated from a single source of potential, the load on the said source oi potential is maintained constant in accordance with my invention by means of an additional tube operated by the fkeying means which places a load on the potential source when the tube or tubes supplied thereby are keyed off and removes said load when the said tube or tubes quency multiplier, or both, B connected at its output to the antenna or transmission line A. 50 The input of B in Figure 1 is coupled as shown to the output of a keyed stage C. In Figure 2 l'.B is coupled at its input to 'an amplier stage 'J which is coupled Ato the keyed stage C. The amplifier stage J of Figure 2 comprises a pair of u electron discharge devices Va and V4. of any type shown, for illustration as being ofthe pentode type, having their control grids I and I' and anodes connected in a push pull amplifier circuit. The anodes of the tubes Vs and V4 are connected in push pull relation by a tuned circuit I0 and are 5 supplied by potentials from a source I2. The screening electrodes 2 and 2 of the tubes V3 and V4 respectively are supplied with direct current potentials from the source I2 by way of similar impedances Z and Z. The suppressor grid elec- 10 trodes 3 and 3 of tubes Va and V4 are also supplied by the appropriate operating potentials from the source I2 by way of other impedances A Z" and Z'". The control grid electrodes I and I' of tubes Vs and V4 are connected as shown by 15 way of coupling condensers Il and I6 and radio frequency choking inductances or impedances RFC and RFC' to the tuned output circuit 22 of a stage C. Operating potentials for the control electrodes I and I' of tubes Vs and V4 are supplied 20 from a source 2li by way of an additional impedance Zu connected as shown. The keyed stage C in both iigures comprises a pair of electron discharge devices V1 and V2 of the pentode type having their anodes connected in push pull rela- 25 tion by the tuned output circuit 22 which 1s connected to a point on the source I2 so that both stages derive their anode potential from the same source, although separate source may be provided if it is desirable. 80

The screening electrodes 2 and 2' 'of tubes V1 and Vn are also supplied with direct current potential from source I2 by way of impedances Z1 and Zz connected as shown. The control electrodes I. and I' of tubes V1 and Vz are supplied 35 with excitation voltage from a source of wave energy E connected as shown by coupling condensers 26 and 28 and radio frequency choke inductances RFC1 and RFC,` to said control electrodes. Operating potentials for the control electrodesl and I of tubes V1 and V2 are supplied from a source 30 connected as shown by way of an additional impedance Z3 between said control electrodes and cathodes of said tubes. The excitation voltages in E may be of any 'frequency 45 appropriate.for signalling purposes and E may be an oscillator or an oscillation amplie or multiplier or both. The voltages from E are relayed and keyed in stage C in a manner described l more in detail hereinafter,l and impressed on B either directly or after being amplified or frequency multiplied or both, in J.

The keying circuit for stage C in both gures comprisesa source of keying current KU connected as shown with an impedance Ri across 5s which the keying potentials may be set up. The impedance R1 is connected as shown between the control grid and cathode of an electron discharge device H. The anode of H is connected to the cathode of H by a potentiometer resistance R3 and an additional resistance Rz. The potentiometer resistance R3 may be shunted by any direct current source D such as a battery or a rectier. A selected point on R3 is connected by a lead 38 and the resistances or impedances Z4 and Z5 to the suppressor grid electrodes 3 and 3' of tubes V1 and V2.

High frequency currents may be shunted around the direct current potential sources connected with the electrodesl, 2, 3 and I', 2', and 3' of tubes V1, V2, V3 and V4 by by-passing con densers C connectedas shown. High frequency potentials appearing in the anode circuits of stages C and J may be shunted around the direct current sources in a similar manner by by-passing condensers C connected as shown.

The keying circuit operates as follows. It may be seen that the suppressor grids are connected to a suitableV point on resistor R3 near the negative end of rectifier D Iin Figures 1 and 2. 'I'he negative terminal of rectifier D is connected to ground through .resistor Rz. The positive` terminal of rectifier D is connected to the anode of tube H. When the keying Unit KU impresses a negative potential on the control grid of tube H the anode current of tube H is blocked and the suppressor grids 3 oftubes V1 and V2 ci the keyed stage C has zerovoltage or a few volts positive potential impressed on them through rectifier D and resistor R2. In this condition the carrier signal is transmitted. When the output voltage of keying unit KU is zero then resistor R1 maintains the grid potential of tube H at substantially zero potential and anode current flows in tube H. 'I'his in effect, connects the positive terminal of rectifier D to ground through the relatively low impedance of tube H. This then causes the potential of the negative end of rectifier D to be relatively high above ground. Consequently a high negative potential is applied to the suppressor grids of keyed stage C. In this case the anode currents in tubes V1 and V2 are cut of! and no carrier signal is transmitted. In this way the transmitter is keyed.

Since the anodes and screen grids of tubes V1 and V2 of'the keyed stage of Figure 1 and the like electrodes of the tubes Vs and V4 of the amplifier stage in Figure 2 draw their direct current from the source I2, a variable load is placed on this sourcel during keying operations. In order to regulate the powerl load I supply any additional compensating or absorbing tube Fhaving its. control grid III connected as shown to the upper terminal of resistance R1,its cathode grounded and its anode l2 connected as shown by way of a resistance R to a positivepoint on the source t2; As will be explained in detail hereinafter the tube draws current when the tubes V1 and V2 are cutoff whereas the tube F is cut ofi when the tubes V1 and V2 draw current.

In some cases it may be desirable to key in one Vstage and compensate in the same stage. In other @cases'it is desirable to key in one stage and comstage, that is, the stage J, by connecting the anode of H and R to the supply lead or source for the anodes and screen grids of V3 and V4.

In'describing more in detail the purpose of my novel compensating circuit and the operation thereof it is noted that where the plate rectifier has a large amount of smoothing it is desirable to accomplish the keying of the transmitter without appreciable variations in the rectifier load. This is accomplished by the use of the compensator tube F which carries in its anode circuit a part or all of the rectifier load when the anode H and tube F by keying unit KU both of these tubes are conductive and signal and anode cur rent is cut oi or reduced in the transmitter stages while normal compensating current flows through the compensating circuit comprising the anode to cathode of F and resistance R. The com'- pensating current is substantially equal to the decrease `in current in the transmitter stagescaused by keying. The tube F absorbs part of the rectifier output voltage of rectifier or source l2 and the resistor R. absorbs the remainder, which is usually the greater part, if the compensating circuitis adjusted correctly. Naturally the tube F and resistor R in the compensating circuit must be correctly selected for optimum results. When the keying unit output is at a high negative potential, the anode current is cut oft' in compensating tube F and keying tube H. In this case anode current flows in the radio frequency tubes of stages C in Figure 1 and C and J of Figure 2 and signalis sent out While the current in the compensating circuit has been cut It can be seen that as described the rectifier load current' and voltage will remain substantially constant, which -was the desired condition. By

connecting R to or near the point on 2 at which the tubes V1 and V2 draw their anode potential, compensation can be primarily accomplished for stage C. By connecting R to or near the point on I2 where the tubes Va and V4 draw their anode potential, compensation can be accomplished primarily for stage J. It is usually most desirable to compensate for the stage which draws the most current or load from the rectifier.

It should be observed that any desirable number of tubes may be operated in parallel at each place Where I have shown a single tube in the circuits of Figure 1 and Figure 2. Moreover, any stage in the transmitter may be keyed which seems desirable. The keyed stages utilize tubes of the pentode type. Tubes of any type such as triodes orfourelectrode tubes may replace the tubes in the stage J or the tubes H and F as long as such other tubes have the desired operating characteristics.

I claim:

1. In a telegraphy system an electron discharge .tube of the pentode type having an input electrode, an output electrode, acathode and a suppressor grid electrode located between said output electrode and the remaining electrodes, alternating current relaying circuits connected with said input and outputelectrodes, a source of potential for maintaining said output electrode positive relative to said cathode, a source of potential for producing operative potentials between said input electrode and cathode, a source of potential and a resistance in parallel connected Ato .said suppressor grid and to said cathode, a

y'put electrodes of said keying tube and thereby vary the potential of said suppressor grid and the ability of said rst' tube to relay alternating current.

2. In a telegraph system an electron discharge tube of the pentode type having an input electrode excited by wave energy to be keyed, an output electrode, a cathode and a suppressor grid electrode located between said output electrode and the remaining electrodes, a source of potential connected to the output electrode for maintaining said output electrode positive relative to said cathode, means for producing operative potentials between said input electrode and cathode, a source of potential and a keying tube impedance connected together and to said suppressor grid and cathode. for maintaining said suppressor grid negative relative to said cathode when said keying tube impedance is relatively low, an additional'A electron discharge tube having its anode and cathode connected to said rst named source of potential said additional tube having a control electrode and means connected with said keying tube and with said additional tube for simultaneously increasing the impedance of said keying tube, thereby, reducing said negative potential between said suppressor grid and` cathode and reducing the impedance of said additional tube to control the operativeness of said first tube and additional tube in an inverse sense.

3. In a telegraphy system an electron discharge tube of the pentode type having an input electrode excited by wave energy to be keyed, an output electrode connected with an output circuit. a

screen electrode, a cathode and a suppressor grid' said` cathode, a keying tube having output electhe operativeness of said first named tube and the operativeness of said additional tube are. controlled in an inverse sense so that the wave energy is keyed at signal frequency and the load placed by said first andadditional tubes on said iirst source oflpotential is substantially constant.

4. In a signalling system an oscillator circuit,

an electron discharge tube including a cathode, a Y

suppressor grid, a control grid, an anode and a shield grid, an input circuit connected between said control grid said cathode and said oscillator circuit, an output circuit connected between said anode and cathode, a source of potential in said output circuit, a second source of potential connected to said cathode, a connection between a point on said second` source of potential and said suppressor grid, a keying tube having a cathode coupled to the cathode of said rst tube and an output impedance connectedv to said second source of potential, means for controlling the impedance of said keying tube in accordance with telegraph signals for controlling the potential applied by said second source of potential to said suppressor grid in accordance with said telegraph signals for correspondingly rendering said oscillator circuit eiective upon said .electron tube system, an additional tube having its outputconnected to said rst named source of potential and means for controlling the operativeness of said additional tube inversely relative to the effectiveness of said rst named electron tube system.

5. In a telegraph system, a pair of electron discharge devices each having a cathode, a control grid, an anode, and `a suppressor grid electrode,

. alternating current relay circuits connected between said anodes and cathodes and said control grids' and cathodes, a source of direct current potential for maintaining said anodes positive relative to said cathodes, a source of direct current potential for producing an operative potential between said control grids and cathodes, a second source of potential connected by a resistance to said cathodes, a keying tube, a circuit connecting the impedance of said keying tube to said second source of potential and said second source of potential to said suppressor grids for maintaining said suppressor grids negative a substantial amount relative to said cathodes when' said keying tube impedance is relatively low,and

means for varying the impedance of said keying tube in'accordance with telegraph signals to varyL the potential of said suppressor grids in accordance with said telegraph signals to control the operativeness of said pair of tubes in accordance with said telegraph signals. i

6. Inra telegraph system, a pair of electron discharge tubes of the pentode type each having a cathode, a control grid, an anode, and a suppressor grid electrode, alternating current relay circuits connected between said control grids and cathodes and between said anodes and cathodes, a source of direct current potential connected be,- tween said` anodes and cathodes, a second source of potential anda keying tube impedance in series, a connection between said series circuit and .said suppressor grid electrodes and said cathodes, a source of keying potentials, said keying tube having a control grid connected to said source of keying potentials to thereby control the impedance of said keying tube in accordance with f said 'keying potential and consequently control the potential between said suppressor grids and l cathodes of said pair of tubesiin accordance with said` keying potentials. A

'7. In a telegraph system, a\pair of electron discharge tubes of the pentode type each having a cathode, a control grid, an anode, and a 'suppressor grid electrode, alternating current relay circuits connected between said control grids and cathodes and between said anodes and cathodes, a source of direct current potential connected between said anodes and cathogdes, a second source of potential, a keying tube having an anode and a cathode and a control grid, a circuit connecting the ano'de and cathode of said keying tube and said second source of potential in a series circuit, a connection between said series circuit and said suppressor grid electrodes and said cathodes, a source of keying potentials connected to the control grid and cathode of said keying tube, and an additional electron discharge device having a control grid connected to said source of keying potentials and an anode connected to said first named source of potential.

8. In a telegraph system, anelectron discharge device of the pentode type having a control grid, a cathode, an anode, and a suppressor grid electrode, alternating current relaying circuits con\ nected between said control grid and cathode and between said anode and cathode, an electron discharge tube amplifier having a control grid and a cathode coupled to the anode of said rst named tube, said amplifier having an anode connected to a source of direct'current potential, a second source of direct current potential, a keying tube impedance and a resistance connected in series with said second source of direct current poten. tial, a second resistance connecting said second 4source of direct current potential to said suppressor grid, a connection between said rst resistanceand the cathode of said electron discharge device, and means for varying the impedance of said keying tube and simultaneously loading and unloading said iirst source of direct current potential.

9. In a telegraph system, a pair of electron discharge devices of the pentode type each having a control grid, a cathode, an anode, and a suppressor grid electrode, alternating current circuits connected between said control grids and cathodes and betweensaid anodes and cathodes, an electron discharge tube amplier having a control grid and a cathode coupled to the anodes of said first named tubes, said amplifier tube having an anode connected to a source of direct current potential, a second source of direct current potential, a resistance in parallel with said second source of direct current potential, connections between the suppressor grid electrodes and cathodes of said rst named pair of tubes and said resistance, a keying tube having its output electrodes connected in series with said second named-source of direct current potential and its input electrodes connected with a source of keying potentials and an absorber tube having its output electrodes connected to said first named source of direct current potential and its input electrodes coupled with said source of keying potentials.

10. In a signalling system an electron discharge device of the pentode type having an input electrode, an output electrode, a cathode and a suppressor grid electrode located between said output electrode andthe remaining electrodes,` an alternating current relay circuit connected between said input electrode and cathode, an alternating current output circuit connected between said output electrode and cathode, means for maintaining said output electrode at a positive direct' current potential relative to said cathode, means for producing an operative direct current potential between said input electrode and cathode, a second source of potential and impedance connected together, means connecting said second source of potential and impedance to said .suppressor grid and to said cathode, a modulator tube. having output electrodes coupled in circuit with said last named source of potential, the connections between said impedance and'suppressor grid and cathode being such that said suppressor grid is negative relativeA to said cathode when the impedance of said modulator tube is low, land means for controlling the potential on the input electrodes of said modulator tube at signal frequency to control the impedance between the output electrodes of said modulator tube and thereby control the potential of said suppressor grid relative to said cathode and consequently the ability of said device to relay alternating current from s aid input circuit to said output circuit.

GEORGE ILIIINDLEY USSELMAN. 

